Project Summary/Abstract: Supplement for Mimicry of Amyloid Oligomers Amyloid oligomers now thought to be the damaging molecular species in Alzheimer's disease, Parkinson's disease, and many other amyloid diseases. Understanding the structures of these oligomers is essential to understanding their mechanism of action, and quite possibly to developing drugs to prevent or treat these diseases. Studying the structures of the oligomers at high resolution is challenging, because the oligomers are heterogeneous and dynamic, forming a variety of sizes and structures that can interconvert. Thus far, the there are no atomic-resolution structures of oligomers of the beta-amyloid peptide, Abeta, the 40- or 42-amino acid polypeptide closely associated with Alzheimer's disease. Grant GM097562 aims to determine the structures of oligomers formed by Abeta by incorporating key fragments of Abeta into macrocyclic beta-sheet peptides designed to mimic the key beta-hairpin building blocks that are thought to make up Abeta oligomers. The PI has determined X-ray crystallographic structures at atomic resolution of trimers formed macrocyclic beta-sheet peptides containing fragments from the central and the C-terminal regions of Abeta. Grant GM097562 aims to build on the discovery of these trimers and the higher-order oligomeric assemblies that they form. The broad overarching goal is to understand the relationship between the atomic-resolution structures of the oligomers and their biological and biophysical properties. To achieve these goals, the PI will synthesize macrocyclic beta-sheet peptides that incorporate different aspects of Abeta structure, determine the X-ray crystallographic structures of the oligomers that these peptides form, measure their cytotoxicity, elucidate their mechanisms of cytotoxicity, and correlate their cytotoxicity and their crystallographic structure by means of biophysical studies of their solution-phase properties. In the course of these studies, an unanticipated opportunity to accelerate our research has emerged. We have discovered that we can generate polyclonal antibodies against our amyloid oligomer mimics and that these antibodies react with molecular entities in the brain tissue of Alzheimer's disease transgenic mice and humans. We believe that these molecular entities are amyloid oligomers formed by Abeta in the brain. This finding is important, because it allows us to more deeply study the biological properties of our amyloid oligomer mimics and better establish their biological relevance. We visualize the interaction of the antibodies with brain tissue by fluorescence microscopy. These studies are limited by access to the high-end confocal microscopes in the Optical Biology Core Facility, which is located in a different building and are heavily booked, thus delaying research. An all-in-one fluorescence microscope will accelerate the research by allowing the rapid imaging of samples on a day-to-day basis, without delays.